Construction of Fe0.64Ni0.36@graphite nanoparticles via corrosion-like transformation from NiFe2O4 and surface graphitization in flexible carbon nanofibers to achieve strong wideband microwave absorption.

Recently, microwave absorption (MA) materials have attracted intensive research attention for their ability to counteract the effects of ever-growing electromagnetic pollution. However, conventional microwave absorbers suffer from complex fabrication processes, poor stability and different optimal thicknesses for minimum reflection loss (RLmin) and widest effective absorption bandwidth (EAB). To address these issues, we have used electrospinning followed by high-temperature annealing in argon to develop a flexible microwave absorber with strong wideband absorption. The MA properties of the carbon nanofibers (CNFs) can be tuned by adjusting annealing temperature, and are dependent on the composition and microstructure of the CNFs. The absorber membrane obtained at 800 °C consists of Fe0.64Ni0.36@graphite core-shell nanoparticles (NPs) embedded in CNFs, formed via a corrosion-like transformation from NiFe2O4 to Fe0.64Ni0.36 followed by surface graphitization. This nanostructure greatly enhances magnetic-dielectric synergistic loss to achieve superior MA properties, with an RLmin of -57.7 dB and an EAB of 6.48 GHz (11.20-17.68 GHz) both acquired at a thickness of 2.1 mm. This work provides useful insights into structure-property relationship of the CNFs, sheds light on the formation mechanism of Fe0.64Ni0.36@graphite NPs, and offers a simple synthesis route to fabricate light-weight and flexible microwave absorbers.

Defect-induced deep red luminescence of CaGdAlO4-type layered perovskites: multi-cationic sites partial/full substitution and application in pc-LED and plant lighting.

A series of CaGdAlO4-type layered perovskite phosphors showing deep red luminescence (λem = 711 nm, λex = 338 nm) were synthesized via a solid-state reaction. A comprehensive analysis performed via photoluminescence, X-ray photoelectron spectroscopy, thermoluminescence, and fluorescence decay revealed that the deep red luminescence is related to oxygen defects and particularly oxygen interstitials. The defect-related luminescence was effectively regulated through partial substitution of multi-cationic sites (the Ca2+ site with Mg2+, Sr2+, and Ba2+; the Gd3+ site with La3+, Y3+, and Lu3+) and full substitution of Gd3+ with Y3+. Remarkably, a 383.3% stronger luminescence was obtained through partial substitution with Lu3+, and the quantum yield of luminescence reached 28.74%, which is higher than those values of most previously reported self-luminescent systems. A pc-LED device was fabricated using this phosphor, and the device was shown to have potential application in indoor plant cultivation.

Non-Small Cell Lung Cancer Detection and Subtyping by UPLC-HRMS-Based Tissue Metabolomics.

Non-small cell lung cancer (NSCLC) is the prevalent histological subtype of lung cancer. In this study, we performed ultraperformance liquid chromatography-high-resolution mass spectrometry (UPLC-HRMS)-based metabolic profiling of 227 tissue samples from 79 lung cancer patients with adenocarcinoma (AC) or squamous cell carcinoma (SCC). Orthogonal partial least squares-discriminant analysis (oPLS-DA) analyses showed that AC, SCC, and NSCLC tumors were discriminated from adjacent noncancerous tissue (ANT) and distant noncancerous tissue (DNT) samples with good accuracies (91.3, 100, and 88.3%), sensitivities (85.7, 100, and 83.9%), and specificities (94.3, 100, and 90.7%), using 12, 4, and 7 discriminant metabolites, respectively. The discriminant panel for AC detection included valine, sphingosine, glutamic acid γ-methyl ester, and lysophosphatidylcholine (LPC) (16:0), levels of which in tumor tissues were significantly altered. Valine, sphingosine, LPC (18:1), and leucine derivatives were used for SCC detection. The discrimination between AC and SCC had 96.8% accuracy, 98.2% sensitivity, and 85.7% specificity using a five-metabolite panel, of which valine and creatine had significant differences. The classification models were further verified with external validation sets, showing a promising prospect for NSCLC tissue detection and subtyping.

Lithium Diffusion in Silicon Encapsulated with Graphene.

The model of a graphene (Gr) sheet putting on a silicon (Si) substrate is used to simulate the structures of Si microparticles wrapped up in a graphene cage, which may be the anode of lithium-ion batteries (LIBS) to improve the high-volume expansion of Si anode materials. The common low-energy defective graphene (d-Gr) structures of DV5-8-5, DV555-777 and SV are studied and compared with perfect graphene (p-Gr). First-principles calculations are performed to confirm the stable structures before and after Li penetrating through the Gr sheet or graphene/Si-substrate (Gr/Si) slab. The climbing image nudged elastic band (CI-NEB) method is performed to evaluate the diffusion barrier and seek the saddle point. The calculation results reveal that the d-Gr greatly reduces the energy barriers for Li diffusion in Gr or Gr/Si. The energy stability, structural configuration, bond length between the atoms and layer distances of these structures are also discussed in detail.

Atomic Identification of Interfaces in Individual Core@shell Quantum Dots.

CdSe@CdS Core@shell quantum dots (QDs) have been widely studied in recent years, due to their architecture which allows to tailor properties by controlling structure and composition. However, since CdSe and CdS have the same crystal structure, same cations, and similar lattice parameters, it is very challenging to image the interface. Herein, high-resolution transmission electron microscopy, high-angle annular dark-field imaging, and energy-dispersive X-ray spectroscopy elemental mapping are combined to characterize the core@shell structure and identify the interface in the CdSe@CdS QDs with different CdS shell thicknesses. By examining changes in lattice spacing in an individual CdSe@CdS quantum dot, the atomic core@shell interface is identified. For thin-shelled QDs, an ideal coherent interface forms between core and shell due to the small lattice mismatch, and the lattice spacing remains unchanged at the core and shell regions. For thick-shelled QDs, the lattice spacing is different at the core and shell regions, while the heterostructured interface is still coherent and cannot be clearly imaged. As the shell thickness further increases, a sharp core@shell interface appears. The results define an approach to characterize the heterostructure of two materials with the same crystalline structure and cations.

Self-Assembly of CsPbBr3 Nanocubes into 2D Nanosheets.

All-inorganic metal halide perovskites have attracted considerable attention due to their high application potentials in optoelectronics, photonics, and energy conversion. Herein, two-dimensional (2D) CsPbBr3 nanosheets with a thickness of about 3 nm have been synthesized through a simple chemical process based on a hot-injection technique. The lateral dimension of CsPbBr3 nanosheets ranges from 11 to 110 nm, which can be tuned by adjusting the ratio of short ligands (octanoic acid and octylamine) over long ligands (oleic acid and oleylamine). The nanosheets result from the self-assembly of CsPbBr3 nanocubes with an edge length of about 3 nm, which possess the same crystal orientation. In addition, an amorphous region of about 1 nm in width is found between adjacent nanocubes. To investigate both the structure and the growth mechanism of these nanosheets, microstructural characterizations at the atomic scale are conducted, combined with X-ray diffraction analysis, 1H nuclear magnetic resonance (1H NMR) measurement, and density functional theory (DFT) calculation, aiming to determine the configuration of different ligands adsorbed onto CsPbBr3. Our results suggest that the adjacent nanocubes are mainly connected together by short ligands and inclined long ligands. On the basis of the DFT calculation results, a relationship is derived for the volume ratio of short ligands over long ligands and the lateral dimensions of CsPbBr3 nanosheets. Moreover, a physicochemical mechanism is proposed to explain the 2D growth of CsPbBr3 nanosheets. Such a finding provides new insights regarding the well-ordered self-arrangement of CsPbBr3 nanomaterials, as well as new routes to synthesize 2D CsPbX3 (X = Cl and I) nanosheets of suitable dimensions for specific and large-scale applications.

Novel superconducting structures of BH2 under high pressure.

The crystal structures of boron hydrides in a pressure range of 50-400 GPa were studied using the genetic algorithm (GA) method combined with first-principles density functional theory calculations. BH4 and BH5 are predicted to be thermodynamically unstable. Two new BH2 structures with Cmcm and C2/c space group symmetries, respectively, were predicted, in which the B atoms tend to form two-dimensional sheets. The calculated band structures showed that in the pressure range of 50-150 GPa, the Cmcm-BH2 phase has very small gaps, while the C2/c-BH2 phase at 200-400 GPa is metallic. The superconductivity of the C2/c-BH2 structure was also investigated, and electron-phonon coupling calculations revealed that the estimated Tc values of C2/c-BH2 are about 28.18-37.31 K at 250 GPa.

Electroic and optical properties of germanene/MoS2 heterobilayers: first principles study.

First principles calculations have been performed to investigate the structural, electronic, and optical properties of germanene/MoS2 heterostructures. The results show that a weak van der Waals coupling between germanene and MoS2 layers can lead to a considerable band-gap opening (53 meV) as well as the preserved Dirac cone with a linear band dispersion of germanene. The applied external electric filed can not only enhance the interaction strength between two layers, but also linearly control the charge transfer between germanene and MoS2 layers, and consequently lead to a tunable band gap. Furthermore, the reduction in the optical absorption intensity of the heterostructures with respect to the separated monolayers has been predicted. These findings suggest that the Ge/MoS2 hybrid can be designed as the device where both finite band gap and high carrier mobility are required.

Micro-nanostructured δ-Bi2O3 with surface oxygen vacancies as superior adsorbents for SeOx2- ions.

Removal of the toxic selenium compounds, selenite (SeO32-) and selenate (SeO42-), from contaminated water is imperative for environmental protection in both developing and industrialized countries. Providing high selectivity adsorbents to the target ions is a big challenge. Here we report that micro sphere-like δ-Bi2O3 (MS-δ-Bi2O3) with surface oxygen vacancy defects can capture hypertoxic SeOx2- anions from aqueous solutions with superior capacity and fast uptake rate. High capture selectivity to SeO32- anions is observed, since the O atoms of SeO32- anions fill the oxygen vacancies on the (111) facet of δ-Bi2O3 forming a stable complex structure. This mechanism is distinctly different from other known mechanisms for anion removal, and implies that we may utilize surface defects as highly efficient and selective sites to capture specific toxic species. Thus, we present a new route here to design superior adsorbents for toxic ions.

In Situ Ligand Modification Strategy for the Construction of One-, Two-, and Three-Dimensional Heterometallic Iodides.

Three heterometallic iodides featuring the novel in situ modified ligands N,N',N″-trimethyl-2,4,6-tris(4-pyridyl)-1,3,5-triazine (Me3tpt3+), N,N'-dimethyl-2,4,6-tris(4-pyridyl)-1,3,5-triazine (Me2tpt2+), and N-monomethyl-2,4,6-tris(4-pyridyl)-1,3,5-triazine (Metpt+), [Pb3CuI10(Me3tpt)] (1), [Pb5Cu2I16(Me2tpt)2] (2), and [Pb3Cu6I14(Metpt)2] (3), were synthesized. Compound 1 exhibits a chain structure, in which the Pb4I16 units are connected by the CuI3 units. The negative charge of the resulting chain is balanced by the cationic Me3tpt3+ groups. 2 features a layer structure, in which the Pb-I chains are connected by the dimeric Cu2 units. The anionic layer is decorated by the Me2tpt2+ motifs via coordinating to the intralayer Cu(I) ions. 3 displays a 3D framework structure, in which the inorganic layer with an 18-membered ring is composed of the strictly alternating arrangements of trimeric Pb3 units and hexameric Cu6 units. The adjacent inorganic layer is further connected by a Metpt+ linker to form the final 3D hybrid framework. It is notable that the in situ N-methylation reaction for tpt has taken place and the resultant motif (Me3tpt3+ for 1, Me2tpt2+ for 2, and Metpt+ for 3) is captured within the corresponding structure. More importantly, the structural diversities from low-dimensional chain and layer to high-dimensional framework is accomplished via the (partial) N-methylation of tripyridine motifs in the heterometallic iodide systems. Our studies offer a new coordination mode of tripyridine motif (N-coordination together with N-methylation) and provide a general strategy to integrate the polypyridine motifs and heterometallic halide systems to generate intriguing hybrid structure and investigate the potential structure-related properties. The UV-vis spectra show that the band gaps for 1-3 are 1.48, 1.35, and 1.34 eV, respectively. Their thermal stabilities have also been studied.

Tuning and understanding the phase interface of TiO2 nanoparticles for more efficient lithium ion storage.

We demonstrate that mixed-phase anatase-TiO2(B) nanoparticles can provide an interesting interphase interface with atomic-level contact for achieving more efficient Li ion storage with high capacity and cycle life. A novel lithium storage mode - "interfacial charge storage in allomorphs" (ICSA) - plays an important role in enhancing Li ion storage.

Structures and electronic properties of the SiAu(n) (n = 17-20) clusters.

The structures and electronic properties of the SiAu(n) (n = 17-20) clusters are systematically investigated using DFT calculations. The result shows that doping with silicon would significantly change the structures of the gold clusters. For the SiAu(n) (n = 17-20) clusters, the lowest-energy structures exhibit shell-like cage configuration in which the dopant Si atom binds to the cage surface and one Au atom skips to the top of the Si atom forming a SiAu5 or SiAu6 subunit except SiAu19, which is a tetrahedron-like structure with a protruding Au atom. The Au atoms of the SiAu(n) (n = 17-20) clusters carry different partial charges due to their different locations.